I am hoping to start a discussion about the effects of headwinds, engine efficiency , and magnetic variations and their effects on the flight plan.

A few questions that I have are:

1) The flight plan was based upon magnetic variations and ground speed so far as I can determine. Airspeed was only relevant in that adjustments were made to achieve ground speed (@150 mph). During flight, reconciliation was required to determine ground speed. Airspeed without verification / calibration without some reference point is irrelevant. If Noonan was adjusting the flight plan based on observations, where is the evidence?

2) The last weather reports were: "Winds east south east about twenty-five knots to Ontario then east to east north east about 20 knots to Howland." Noonan measured 23 knots and it was reported by radio to Lae. From this we can guess that winds aloft were in the range of 22-25 knots. If there have been studies about the headwinds that contradict these findings can you please point me to the documents that suggest otherwise?

3) The Lockheed and Pratt and Whitney documents suggest that 5,000 ft was the optimal altitude for conserving fuel. While a lower wind speed might have achieved higher efficiency the flight plan was based on 150 mph. Is there any documentation that suggests that Earhart planned to travel at a different altitude? Is there any evidence that the flight plan would have been modified en route based upon land or celestial observations?

The "must be on you but cannot see you" message was received at 1912 GMT. Your calculation of how much stronger the winds were than Fred predicted or observed will depend on where you place the aircraft at that time.

"Finally, just before 8:00 PM aboard Itasca, official notification of Earhart’s departure arrived from Lae, via Samoa: 'Urgent, Black, Itasca . . . Amelia Earhart left Lae at 10 AM local time July 2nd. Due Howland Island 18 hours time.' This information presented a new picture. The plane had left Lae two hours earlier than previously reported, and the eighteen-hour time-en-route estimate indicated that Earhart anticipated lighter headwinds than predicted in the most recent forecast. Itasca should now expect the plane to arrive at around 6:30 AM" (Finding Amelia, p. 85).

The original flight plan was for 18:00 flight time? I thought it was based upon the Howland to Lae flight plan requiring 17:01 hours?

You will have to read between the lines of the meagre material available.

The way that I interpret the sources I gave you is that someone started with the still-air estimate of 17 hours, factored in an estimate of the strength and direction of winds aloft, and came up with the 18 hour estimate relayed to the Itasca--that is what I meant by "original," as distinct from the 1912 GMT message that says, "We must be on you but cannot see you." I don't know who came up with the 18 hour calculation. The Chater Report says that "Miss Earhart did not receive any weather reports on July 2nd prior to her departure."

Please note that this is not a new question by any means. Here is an excerpt from the 1999 version of the Forum:

Date: Mon, 4 Jan 1999 11:58:10 ESTFrom: Andrew McKennaSubject: Winds

Observations taken at Howland that morning were:

Surface - ESE at 16 knts

1,000 ft - ESE at 15 knts

2,000 ft - E at 17 knts

Applying these winds to AE flightplan, what effect would we expect on AE's flight path to Howland? Would she end up farther WNW than expected, or have I got it wrong?

Were these winds factored into the statistical analysis of most likely ending locations that was presented to us at the AE Symposium in Delaware a couple of years ago?

Just curious.

AMCK 1045C

***************************************************************

From Ric

We need to remember that these were the winds at Howland on the morning of July 2nd. They may or may not resemble the winds encountered hundreds of miles to the west during the preceding night. Also, whatever the winds, there is no reason to think that they blew the flight off course. That's what a navigator does - keep the flight on course by adjusting the heading to compensate for winds. There is no reason to think that Noonan was not able to assess the flight's progress by means of star sightings during the night.

The Monte Carlo projections done by Wagner Associates took all of the known factors into account but there were way to many unknown factors to permit a high degree of probability for any location. The best they came up with was that the flight probably ended up south of Howland and perhaps a bit short of the line of position passing through Howland. (Do I have that right Randy?)

GL makes the argument that Fred would have planned to intercept the LOP north of Howland. That is a shorter distance to fly, and doesn't involve any "back tracking", so to speak. When Jacobson and others have attempted to reconstruct the flight, do they assume Fred was trying to navigate directly to Howland, or do any of them include an offset?The argument has been previously made that the flight may have planned to intercept the LOP northwest of Howland, so they turned "right" expecting this would bring them closer. How long would they continue after their right turn before, um, plan-B?

JohnIf the "flight plan" was just to reverse the plan developed for the first attempt ( a great circle route from Howland to Lae of 2556 sm with an estimated flight plan of 17.01 hours ( yes, someone actually thought that he could estimate flight time within 0.01 hour, 0.6 minutes),then they would have planned a 16 waypoint great circle route Lae to Howland

GL makes the argument that Fred would have planned to intercept the LOP north of Howland. That is a shorter distance to fly, and doesn't involve any "back tracking", so to speak. When Jacobson and others have attempted to reconstruct the flight, do they assume Fred was trying to navigate directly to Howland, or do any of them include an offset?The argument has been previously made that the flight may have planned to intercept the LOP northwest of Howland, so they turned "right" expecting this would bring them closer. How long would they continue after their right turn before, um, plan-B?

I have been using a 60 NM offset in my examples and the length depends on the time that Noonan got his last fix. If his last fix was at 1627 Z, the report of "partly cloudy," then the maximum uncertainty in his DR was 46 NM using the normal 10% of distance flown estimate of DR uncertainty or 70 NM using the most pessimistic estimate of DR accuracy. If he got a fix later, the the offset would be smaller. During this process you do not abandon your DR. By aiming off to one side by the amount of the estimated maximum error in the DR at the point of interception (60 NM in this example) you have converted a 120 NM uncertainty along the LOP, 60 NM left and 60 NM right, into a 120 NM uncertainty extending 120 NM left and zero right. This ensures that you do not end up to the right of the destination. This allows for the maximum possible error but, in fact, you are more likely to be nearer to your DR position than to the extreme edges of the you intercept your aiming point 60 NM to the left you are not surprised that you don't see the island since it is most likely to be about 60 NMto your right. As you fly along the LOP your DR also moves along the LOP getting closer to where the island should be and you expect to see it as you approach that point. Even if you don't see it when you arrive there you are not yet worried because it can still be ahead of you. But as you continue further and further along the LOP after the DR put you over the island you start getting worried. But you must still proceed out the whole 60 NM past where the island should have been to be certain that you do not miss the island. At the end of that leg you would know that you have missed the island and would have to deal with that problem, most likely planning a standard expanding square search pattern centered on the most likely point for the island. So he would not have flown beyond 60 NM past Howland before turning around and starting a search pattern. He would not have continued SSE any further.

GL makes the argument that Fred would have planned to intercept the LOP north of Howland. That is a shorter distance to fly, and doesn't involve any "back tracking", so to speak. When Jacobson and others have attempted to reconstruct the flight, do they assume Fred was trying to navigate directly to Howland, or do any of them include an offset?The argument has been previously made that the flight may have planned to intercept the LOP northwest of Howland, so they turned "right" expecting this would bring them closer. How long would they continue after their right turn before, um, plan-B?

I have been using a 60 NM offset in my examples and the length depends on the time that Noonan got his last fix. If his last fix was at 1627 Z, the report of "partly cloudy," then the maximum uncertainty in his DR was 46 NM using the normal 10% of distance flown estimate of DR uncertainty or 70 NM using the most pessimistic estimate of DR accuracy. If he got a fix later, the the offset would be smaller. During this process you do not abandon your DR. By aiming off to one side by the amount of the estimated maximum error in the DR at the point of interception (60 NM in this example) you have converted a 120 NM uncertainty along the LOP, 60 NM left and 60 NM right, into a 120 NM uncertainty extending 120 NM left and zero right. This ensures that you do not end up to the right of the destination. This allows for the maximum possible error but, in fact, you are more likely to be nearer to your DR position than to the extreme edges of the you intercept your aiming point 60 NM to the left you are not surprised that you don't see the island since it is most likely to be about 60 NMto your right. As you fly along the LOP your DR also moves along the LOP getting closer to where the island should be and you expect to see it as you approach that point. Even if you don't see it when you arrive there you are not yet worried because it can still be ahead of you. But as you continue further and further along the LOP after the DR put you over the island you start getting worried. But you must still proceed out the whole 60 NM past where the island should be to be certain that you do not miss the island. At the end of that leg you would know that you have missed the island and would have to deal with that problem most likely planning a standard expanding square search pattern centered on the most likely point for the island. So he would not have flown beyond 60 NM past Howland before turning around and starting a search pattern. He would not have continued SSE any further.

I was looking over the radio reports from EA after they departed Lae and found a couple of interesting observations. If we look at the log soon after they departed Lae, they gave a couple of reports with position from which we can take a rough guess at their ground speed achieved.

From what I can see, they departed Lae at 10:00am local time which was 0000 GMT.

From that Chater Report:

The next report was received at 3.19pm (0519 GMT) on 6210 KC – “HEIGHT 10000 FEET POSITION 150.7 east 7.3 south CUMULUS CLOUDS EVERYTHING OKAY”

If we plot these coordinates on Google Earth it is clear that she was far South of the position she should have been at if they were following the original flight plan (in reverse from the Howland to Lae flight plan calculated for them). Given that there were reports of intense storms due East of Lae at about 300 miles out, this makes perfect sense that she must have been able to avoid this storm by heading South-East then turning North East to get back to the original flight plan. The length of this journey was 257 miles from Lae on a 99.07 heading. They probably steadily climbed to 10,000ft during this segment so as to conserve fuel. For simplicity, let’s call this position check point A.

The next report received at 5.18 pm (0718 GMT) “POSITION 4.33 SOUTH 159.7 EAST HEIGHT 8000 FEET OVER CUMULUS CLOUDS WIND 23 KNOTS”

Let’s call this check point B. Plotting this position on Google Earth, assuming they traveled in a straight line from A to B, they would have passed directly over Nukumanu Island. This would have allowed them to measure their actual ground speed so that the head winds could be determined. Her report includes the headwinds that they measured at 23 knots which is very close to the forecasts and the observations taken that day. This may have been a very accurate measure for that point in time as well. Granted they might have changed their air speed on the journey to Howland, we can be fairly certain that she had a very good idea of the headwinds and would have adjusted her airspeed accordingly to get back to the flight plan. Another very interesting point is that when she reported this position, she was within 4 miles (off the port side) of the original flight plan vector from Lae to Howland. The heading from her previous report was 72.16, the distance was 652 miles.

There is a bit of a problem here from what I can see so far as the time stamps in the Lae radio log is concerned. The time between reports was only 2 hours yet they traveled 652 miles. For this to be true, they would have had to be traveling 326 MPH (ground speed) between check point A and check point B. This must be incorrect. If we assume that perhaps the first time stamp is incorrect but the second time stamp is correct (7 hours and 18 minutes since departing Lae), this would produce an approximate ground speed of 124.5 mph from as they progressed from Lae to check point A and then to check point B. If we now make the assumption that until check point B was encountered, and a land reference was used to estimate air speed, they were not adjusting for head winds. If we make this assumption, and we add the 23 knot head wind, this works out to an airspeed of 151 mph (at sea level), and a rough estimate of 126 mph indicated airspeed at 10,000ft (2% per 1000 feet).

If we now compare the actual flight plan to when they arrived at check point B, this was at a point about 890 miles on the original flight plan path that had assumed a ground speed of 150 mph, this works out to about 5 hours and 56 minutes en route on the original flight plan. This means that they were behind schedule, 1 hour and 22 minutes according to the original flight plan. What is also interesting here is that looking at the original flight plan, 890 miles out from Lae; they would have been in the 5 segment of the flight plan (assuming that they used the original Howland to Lae flight plan, reversed). This would have been at a point 155 miles out on a 175 mile segment. Assuming that they stayed on the same course and speed as they did from point A to point B, they would have intersected the original flight plan path in 33.2 miles or roughly within 16 minutes where the next segment in the original flight plan would begin.

I would venture to guess that for the remainder of the flight, having bypassed the storm and intercepted they original flight plan path, they would have continued on to Howland adjusting for a 23 mph head wind until some observation proved otherwise. I would also dare to guess that they would have quickly chosen a new ground speed for the remainder of the journey to Howland that they wanted to achieve and adjusted the times on the original flight plan accordingly. Since they had strayed from the original flight plan, re-calculation of the time per segment and ground speed achieved was not an option, it was a necessity.

While it is certainly possible that Fred could have recalculated the time for each segment based upon the speed actually traveled, I cannot see any compelling reason to adjust your flight plan unless navigation computations proved that you made a serious error. In order to simplify the remainder of the flight, they probably adjusted the manifold pressure and RPM as needed in order to achieve the desired ground speed at a given altitude and that they did not pore over the Lockheed documentation to re-compute optimal speeds based on the changing weight loads prior to the segment change in the flight plan. While it is entirely possible to do so, doing so could add un-necessary risks for introducing error in to the flight plan. Since they felt confident that they had enough reserves as was the case in AE's previous flights, adjusting the flight plan over and over makes little sense. They had enough on their plate, maintaining accurate timing, achieved ground speed, along with the magnetic heading on the flight plan. Fred would have also been busy looking out the window taking observations (hopefully) along the way.

If we go back to the radio log, when they were within radio range of the Itasca, the only approximate distance that we can be pretty sure of was the report at 200 miles out.

Earhart said at 1744GMT: About 200 miles out, approximately.

While this report was given around her regularly scheduled broadcast, and it would be very coincidental to be exactly 200 miles out, we can probably assuming that they were pretty close to that measure according to where they thought they were at that point in time. If we assume that this distance was approximately correct, and that they were following the original flight path, the distance traveled from check point B to this 200 miles out check point (C), this would have been approximately 1474 miles along the original flight path. If this were true, this implies that they would have achieved about a 141.3 ground speed during this segment of the flight. If they had assumed a 23 knot headwind, this would mean they indicated air speed was roughly 167.75 mph at sea level, 145 mph at 8,000ft (for the bulk of that journey). While this speed would not be ideal according to the Lockheed documentation, this would suggest that they were not adjusting their plan to optimize for gross weight and did indeed choose a fixed speed for the remainder of the trip from check point B to Howland. Perhaps the elevation of 8,000 ft was not an arbitrarily chosen altitude but was selected based on the telegram from Johnson (at Lockheed) to Lae. They just happened to find themselves at 8,000 ft at Nukumanu Island and they might have stayed there. Since they had to account for a headwind, the remainder of the recommendations (manifold pressure and RPM) would be impossible as the recommendations from Johnson must have been made for zero headwinds. One thing we can be fairly sure of is that they would experience greater efficiency at 8,000 ft than at sea level for the remainder of the flight.

As a footnote here, it is not so important that they were actually 200 miles out and headed directly for Howland, what is important is that they thought they were 200 miles out based upon following the flight plan and tracking their time. Since we know that they did not make it to Howland, we can guess at a few possible causes as to why they were not where they thought they were:

I think it is pretty safe to guess that we can rule out #1 and #2 for the most part. Tracking time is hardly debatable and following a compass heading were probably easiest tasks that they were performing.

Breaking down #3, there are perhaps a few possible scenarios:

1) Mis-calibrated or inaccurate altimeter.2) Translations from Fred's knots per hour navigation to miles per hour needed by Earhart was incorrectly computed or Fred assumed that Earhart was performing the conversion (wouldn’t that be tragic).3) Incorrectly accounting for head winds.4) Computations to compute true airspeed were not computed correctly or were too course be useful.

What about a mis-calibrated altimeter? Do any of the maintenance records from Lae or previous trips suggest that the calibration was checked? Just as a guess, the readings would have had to been over 1000ft off or more to have a real impact. This seems an unlikely culprit.

Ignoring #2 as this should have been a trivial task for Noonan, accounting for head winds (#3) should have been fairly straight forward. If we assuming that they were correctly subtracting the head winds from the measured speed and Earhart reported a headwind of 23 knots at Nukumanu Island, they were probably correctly attempting to account for the headwinds (until Fred's navigation proved otherwise). If they had overestimated the headwinds, and the indications are that the winds were actually more favorable than 23 knots, the travelers would have under estimated their ground speed achieved. This would have affected when magnetic course adjustments were made. Has anyone attempted to compute how far off course the miscalculation of headwinds might have affected their estimations assuming that they were accurately tracking true air speed at altitude? This should be fairly easy to do using the actual observations compared to the 23 knots that Earhart announced. If the ground speed achieved calculation was over estimated by just 2% from check point B to Howland, this would have accounted for a 29.25 mile error by the time you reached Howland. Over estimate your ground speed by 4% and you are well over the horizon short of Howland.

As far as the computing the true air speed based on altitude goes, what was the common practice of the day? Was it typical to use charts and tables or some simple approach like 2% per 1000ft? Was there any evidence that Fred brought with him a flight computer like the E-6B that would have been available in that era to simplify the headwinds and true air speed calculations? Is there any photographic evidence that such a computer did exist?

If any of the above errors could account for a miscalculation that would have landed them outside of the 40 mile radius from Howland (over the horizon), it is probably worth speculation.

Perhaps as others have mentioned, it was perhaps a series of small miscalculations that added up to one large error. Large enough to have them miss Howland anyway. Perhaps it would be interesting to create a list of tolerance combinations (true air speed, head winds, magnetic course) that must have been held in order for them to have found Howland (within say 15 miles) without help. That may be an interesting exercise in and of itself.

The length of this journey was 257 miles from Lae on a 99.07 heading. The heading from her previous report was 72.16, the distance was 652 miles.

I have attached a photo of Earhart's compass, it is the object mounted above the Cambridge instrument, above the instrument panel centered in front of the windshield. It has a mark every five degrees and the photo shows it indicating a compass heading of about 300 degrees. Look at this photo and tell me the method you would use to maintain your compass heading of 99.07° or 72.16°, an accuracy of one-one-hundredth of a degree. And just to add some more realism to the question, remember that the compass card dances around a bit in flight. gl

As a footnote here, it is not so important that they were actually 200 miles out and headed directly for Howland, what is important is that they thought they were 200 miles out based upon following the flight plan and tracking their time. Since we know that they did not make it to Howland, we can guess at a few possible causes as to why they were not where they thought they were:

I think it is pretty safe to guess that we can rule out #1 and #2 for the most part. Tracking time is hardly debatable and following a compass heading were probably easiest tasks that they were performing.

Unless they found themselves completely dependent on the magnetic heading once they realized celestial observations were unavailable.

Imagine this for a moment; they lose celestial readings; find a discrepency between the DG (previously calibrated directional gyro) and magnetic compass. What to do? Re-calibrate for magnetic or continue in true course? How accurate (or incaccurate) was the DG's precession? Did they have numbers for both variation and deviation - and if so, how accurately calibrated were they? It seems that the magnetic variation was in the neighborhood of 9 degrees for most of the trip. If that was lost or not accounted for, how far off would they be?

What if Amelia made the human-error of of flip-flopping the 9 degrees in the wrong direction. Since they were in a remote part of the world, it may have been a factor. Reverting back to basic flight navigation for magnetic compensation may not have been something she was accustomed to.

As a footnote here, it is not so important that they were actually 200 miles out and headed directly for Howland, what is important is that they thought they were 200 miles out based upon following the flight plan and tracking their time. Since we know that they did not make it to Howland, we can guess at a few possible causes as to why they were not where they thought they were:

I think it is pretty safe to guess that we can rule out #1 and #2 for the most part. Tracking time is hardly debatable and following a compass heading were probably easiest tasks that they were performing.

Unless they found themselves completely dependent on the magnetic heading once they realized celestial observations were unavailable.

Imagine this for a moment; they lose celestial readings; find a discrepency between the DG (previously calibrated directional gyro) and magnetic compass. What to do? Re-calibrate for magnetic or continue in true course? How accurate (or incaccurate) was the DG's precession? Did they have numbers for both variation and deviation - and if so, how accurately calibrated were they? It seems that the magnetic variation was in the neighborhood of 9 degrees for most of the trip. If that was lost or not accounted for, how far off would they be?

What if Amelia made the human-error of of flip-flopping the 9 degrees in the wrong direction. Since they were in a remote part of the world, it may have been a factor. Reverting back to basic flight navigation for magnetic compensation may not have been something she was accustomed to.

Thoughts?

What you are saying is the equivalent of saying that neither Earhart nor Noonan were capable of pouring piss out of a boot with the instructions printed on the heel.

As far as the computing the true air speed based on altitude goes, what was the common practice of the day? Was it typical to use charts and tables or some simple approach like 2% per 1000ft? Was there any evidence that Fred brought with him a flight computer like the E-6B that would have been available in that era to simplify the headwinds and true air speed calculations? Is there any photographic evidence that such a computer did exist?

I read the report from the Waitt search and I have many criticisms of their search methodology. On Page 48-49 their report states that no handy calculators were available to make the conversions between indicated airspeed, true airspeed and ground speed until the invention of the circular slide rule type flight computer E-6B in World War Two. The report is only off by one World War. These devices were developed as early as 1910 and found wide use in WW I. The Dalton MK VII was perfected in 1932 and the Jensen in 1933. These were easy to operate and performed the required calculations. With slight modification the Dalton became standardized as the E-6B in WWII. So AE most likely could have made these calculations by herself in the cockpit. Further. Noonan wrote that he had the Dalton MK VII in his letter to Weems which I have attached.

Copyright 2019 by TIGHAR, a non-profit foundation. No portion of the TIGHAR Website may be reproduced by xerographic, photographic, digital or any other means for any purpose. No portion of the TIGHAR Website may be stored in a retrieval system, copied, transmitted or transferred in any form or by any means, whether electronic, mechanical, digital, photographic, magnetic or otherwise, for any purpose without the express, written permission of TIGHAR. All rights reserved.